In vertical type wood shearing machines, the blade-holding unit and the bar-carrying unit are provided, in the production step, with a feeding motion towards the wood stock, having an extent equal to the thickness of the sheet cut.
During such feeding motion, in order to avoid that the wood stock, which is also moving, interferes with the blade, it is necessary to provide also suitable means to rapidly move away and subseqently move closer to the wood stock itself.
In the machines known heretofore in the art, said means to disengage the blade from the wood stock --which intervene during the return stroke of said wood stock --consist of a types of motions which allows for rotation, successively in both directions, of the blade-holding unit and the bar-carrying unit about an axis which is located above the supporting slides and is parallel to the blade.- As a result there is a lack of total rigidity between the side slides of the wood shearing machine and the blade-holding unit and bar-carrying unit in the cutting step,, during which said members have to be kept stationary.